1. Field of the Invention
The present invention relates to an elastically deformable antenna reflector for a spacecraft, such as an artificial satellite or space probe.
2. Description of the Related Art
It is known that the items of equipment, such as the antenna, solar panels, etc, associated with a spacecraft have to be able to be folded in order to be able to be accommodated in a launch vehicle (rocket, shuttle) and to be deployed after ejection out of said launch vehicle, so as to take up their operational configuration.
It is known, moreover, that such equipment has already been produced in such a way that it is elastically deformable, this equipment then being able to take up either a deployed state, or a folded state, elastically deformed. By way of example, mention may be made of:
the U.S. Pat. No. 3,521,290, which describes an antenna reflector in a single piece of an elastically deformable material provided with a rigid central base to which are linked a plurality of radial ribs integral with the convex face of said reflector and elastically articulated to said central base. Thus, said antenna reflector can take up a position folded into the shape of a tulip, which does not risk entailing a permanent deformation of said reflector, and the change from the folded position into the deployed position in the shape of a concave disk can be carried out under the action of the elastic energy stored during the folding of the antenna structure. Controllable retaining means, consisting of a belt with pyrotechnic bolts surrounding said folded reflector and arranged on the opposite side from said central base, are provided in order to hold said reflector and said radial ribs in the folded position under stress; PA1 the U.S. Pat. No. 4,133,501, which describes a solar panel in a single piece for a spacecraft produced in an elastically deformable way in order to take up either a curved folded position under stress in which said solar panel matches the convex outer surface of said spacecraft, or a flat deployed position, clear of said outer surface, the change from the curved, folded position to the flat, deployed position being due to the elastic relaxation of said solar panel. In the curved folded position, the solar panel is held against the outer surface of said spacecraft by latches, carried by the spacecraft; and PA1 the U.S. Pat. No. 4,926,181, which describes an antenna reflector in a single piece of an elastically deformable material, which can be rolled into a cylindrical shape and held in this shape by clamps. An underlying pliable structure can be deployed, in order to serve as a support on which said reflector can unroll and take up its deployed, operating shape, under the action of its elastic relaxation. PA1 outside said casing, said reflector can take up a stable, deployed state without elastic stress, corresponding to its functional shape; PA1 within said casing, said reflector, by elastic folding around said axis of the casing, can take up a folded state allowing it laterally to envelop said body, said reflector being held in this folded state by virtue of controllable retaining means; and PA1 the change by said reflector from its folded state to its deployed state being due at least in part to the release of the energy stored in said reflector when it was elastically folded in order to make it change from its deployed state to its folded state, PA1 in that said reflector is separated into two parts by opposing slot edges; and PA1 in that, in the folded position of said reflector, said opposing edges of said reflector parts move with respect to one another so as to bring said protruding peripheral part of the reflector closer to said longitudinal end of said body. PA1 the U.S. Pat. No. 3,176,303 already describes an antenna reflector comprising a rigid central base, from which a plurality of petals, in the form of sectors, extend radially, constituting the reflector of the antenna, each of said petals being produced from an elastically deformable rigid material, in order to be able to take up either a bent position under stress, which corresponds to the folded storage position of said reflector, or a position spontaneously deployed in the form of a concave disk, which corresponds to the deployed operating position of said reflector, the change from the folded position to the deployed position being due solely to the elastic relaxation of said petals, previously elastically bent. In the folded position, the opposing edges of adjacent petals overlap in pairs, and controllable retaining means, of the peripheral belt type, are provided to keep said petals together in the folded position of the reflector. PA1 the U.S. Pat. No. 5,574,472 and the patent EP-A-0 534 110 describe an antenna reflector in a single piece of an elastically deformable material, which can take up a folded position in the form of a bowl by virtue of a controllable-breaking tension link arranged between two diametrally opposed points on the periphery on said reflector. It will be noted that, in this bowl-shaped folded position, the upper peripheral edge of the reflector, protruding with respect to the body of the spacecraft, is straightened outwards and cannot therefore be accommodated in the conical part of the casing. PA1 the first special feature of the present invention consisting in producing said elastically deformable reflector in a limited number of parts which can be partially superposed along their opposing edges makes it possible: PA1 the second special feature of the present invention consisting in fixing said reflector in the folded position on the body of said spacecraft makes it possible:
Moreover, as demonstrated, for example, by the U.S. Pat. No. 5,644,322, it is usual, for launching said spacecraft, to store it in an elongate casing, for example of cylindrical-conical shape, constituting, for example, the upper nose cone of the launch rocket, the reflector of the antenna or antennae of said spacecraft being arranged laterally with respect to the body of the latter in the peripheral space defined between said body and said casing. In this prior document, the antenna reflector consists of a central rigid base of large surface area surrounded by a peripheral frustoconical ring produced from an elastically deformable material. Hence, by virtue of such a structure, the size of the reflector, within said cylindrical-conical casing, can be slightly reduced by temporarily elastically deforming said peripheral ring, said reflector then taking up the shape, at least approximately, of a bowl laterally encasing said body. The reflector is kept in this bowl shape by a belt, loosening of which is controlled electrically and which surrounds said body and said reflector at the center of said base, this belt folding said elastically deformable ring down onto said body, bearing on two diametrally opposite points of said ring. After ejection in space, said reflector can resume its operating position, by removal of said belt and elastic return of said peripheral ring to its elastically relaxed, stable, deployed position.
It can easily be understood that, in such a device, the saving in size of said reflector in the folded position, by comparison with the deployed position, is limited. This is because, on the one hand, because of the large diameter of said rigid central base, the lateral compression of the reflector can be applied only to the peripheral ring, such that the saving in the lateral size is relatively small. Moreover, this lateral compression not only exerts no reducing action on the longitudinal dimension of said reflector, but also increases said dimension due to the fact that it entails the straightening of the upper part of said peripheral ring outwards. The longitudinal size of the reflector, in the folded position, is thus greater than that of its deployed position. Because of its dimensions, said reflector generally overshoots the upper longitudinal end of the body of said vehicle housed in the cylindrical part of the casing and has to be extended into the conical part thereof. This conical shape thus imposes a limitation on the diameter of the reflector. However, for obvious reasons of performance, it would be advantageous for the reflector to be able to have as large a diameter as necessary, and to match the convergent shape of the conical part of the casing.
Moreover, it will be noted that, in the folded position, the reflector of the U.S. Pat. No. 5,644,322 is not held firmly, such that it is subject to the vibrations induced during the launch. This can result in difficulties of dynamic balancing and of damping of the vibration of said reflector, and even damage to the reflector or to the surrounding objects.